Question

a block of wood of length 50 cm and area of cross section 10cm^2,floats in water wit 3/5 of its length above water. calculate density of wood in gcm^3

Answer 1

Focal length of concave lens = -50 cm

= m

= -0.50 m

To find: Power of lens?

We know,

Power of lens = - 2 Dioptres.

Since the focal length of a concave lens is always negative so power of the concave lens is -2 diopters.

Answer 2

Given that,

Length of block of wood, l = 50 cm = 0.5 m

Area of cross section, $A=10\ cm^2=0.001\ m^2$

It floats in water wit 3/5 of its length above water

To find,

The density of wood.

Solution,

Relative density of an object is given by volume of body immersed divided by total volume of body. It is given by :

$d=1-\dfrac{3}{5}\\\\d=\dfrac{2}{5}$

So, the density of wood is given by :

d = (2/5) × density of water

$d=\dfrac{2}{5}\times 1\ g/cm^3\\\\d=0.4\ g/cm^3$

So, the density of wood is $0.4\ g/cm^3$.

Learn more,

Density

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